Within the field of metal cutting tools used in groove turning and groove milling operations, cutting inserts removably securable in an insert holder have long since provided a way of performing a cutting operation with a suitably hard material, i.e. cemented carbide, in the vicinity of the cutting edge, where the insert holder, manufactured from a less hard material, is reusable following the disposal of a worn or damaged cutting insert.
This type of cutting tool has been further developed to utilize indexable cutting inserts with an increased number of cutting edges, giving economic benefits from providing an increased number of cutting operations per cutting insert. This type of cutting tool has also been developed to provide a more efficient means of securing the indexable insert to the insert holder.
U.S. Pat. No. 4,461,602 discloses a milling cutter consisting of a shaft, a cutter plate and a screw bolt by means of which the cutter plate is detachably fastened at the front end of the shaft. The latter has a recess in the front face thereof. The recess is defined by three planar side faces leaving a peripheral gap between each pair thereof. The cutter plate substantially formed triangularly is fitted in the recess for being immovable in a radial plane. Protrusions of the cutter plate protrude through the gaps and are provided with a cutting edge respectively.
U.S. Pat. No. 5,607,263 discloses a cutting plate having a disk-shaped body with three teeth and a single integrally formed projection. The holder has a front-face recess which is encompassed all around by a wall of the holder. As shown in FIGS. 5 and 6 of U.S. Pat. No. 5,607,263, the projection has a coupling surface with the contour of a triangular convex polygon and the recess has a counter-surface with the contour of a triangular concave polygon, and in a loaded state three contact zones are formed between the coupling surface and the counter-surface.